Checking Your Home For Structural Damage After An Earthquake

Learn how to safely and thoroughly inspect your home's exterior shell, foundation and interior, for structural damage following an earthquake.

Earthquake forces can damage the structure of your home in mere moments with a variety of motion. These include jolts, upheavals, drops, horizontal back-and-forth or side-to-side shaking or both, rolling and bouncing. The intensity and damage sustained will be determined by the type of geology your home rests upon and the type of materials it's built with. Wooden structures are more flexible and more able to withstand the violent shaking of quakes, while masonry buildings, especially those unreinforced, can crumble. After a quake, once you have made sure that your family is safe and evacuated, you can proceed with structural damage checks.

Expect aftershocks during your inspection. It's best to do inspections from a distance using a flashlight, starting with the exterior. Most structures are wood framed with plywood sheathing, or wood framed with concrete or masonry walls, steel posts and beams. All of these elements can sustain damage. Some of this will be apparent. Some will remain hidden. Your task is to spot the indicators.

The first step is to shut off any leaking gas lines at the main shutoff valve. If water lines are broken, shut these off as well.

Do a visual check of all sides of the structure. Framing damage will show through stucco, plaster or wood sheathing reflecting internal damage. Some cracking is inevitable. Cracks 1/8-inch or larger are bad signs. The more severe the crack on the exterior surface, the more damage sustained to hidden framing.

Stand 20 to 30 feet away and check the walls for plumb from top to bottom. Horizontal quake movements can separate and break stud frames. Displacements of an inch or more may indicate this type of structural damage. Broken windows or frames are obvious, but sometimes walls shake without windows breaking and the damage is harder to spot.

Check the roofline. Is the chimney still attached, does it lean away from or has it fallen completely away from the structure? Loosened bricks or the entire chimney can come tumbling down during aftershocks. Is the roof intact or displaced? Buckling indicates problems.

Inspect the sides of your home for loosened or separated brick veneers. Check the sheathing. Is it bulging, bowed or broken? Are nails popped out? Have gaps appeared larger than 1/8-inch between plywood sheets?

Check the exposed lower walls atop the foundation. Are they still attached to the house or has the house slipped off? During a quake the horizontal shaking forces slam the foundation back and forth while the frame moves in an opposite direction. This shearing can break the structure loose from the foundation.

You'll most likely see cracks in the foundation. Hairline cracks are nothing to be concerned about. But deeper or larger cracks in blocks can be an indicator of a shifted foundation. Broken bricks or blocks are almost a sure thing and crumbling blocks are a certainty. Use your flashlight to peer into the larger cracks. If you can see that the crack is deeper than 1/8-inch, clean through or that concrete has cracked off and exposed steel reinforcing, then the foundation has sustained severe damage. If you can see any bent or twisted steel or wooden I-beams, or see framing bolts that once secured the frame to the foundation now broken or missing, the foundation is severely damaged.

If you see any major structural damage, it may not be safe to enter your home. If you have any doubts about safety, under no circumstances should you reenter your house. Stay outside and call a city building inspector. But if you do not see any structural damage, start an inspection of the interior.

Check load-bearing walls and members. Are they still intact or have they shifted or snapped? Check support posts to see if they are cracked or damaged. Have the ceilings begun to pull away from them? How about partitions? Remove some ceiling panels to check the framing. Check the stairwells to see if they are still connected to the frame. Gaps are not good signs. Cheek the floors to see if they have pulled way from the frame near the walls or heaved upward. Inspect the walls for plumb. Walls that are bowed, cracked or are otherwise offset means you have damage. Look for nailheads popped loose from wallboard. A few are OK, but many are a bad indicator that twisting motion has displaced the walls.

In the attic check trusses and diagonal braces for buckling, bows, cracks, or breaks. Inspect the tops of walls where they meet the attic supports to see if they are still connected. Do the same with the roof. Are tanks, plumbing and electrical installations still intact? If you see any daylight, it's best to get out.

If you're fortunate to not have sustained any damage, go through the house and turn off electrical appliances, computers, TVs, and lights they may have been left on to prevent any surge damage when the power is restored. Hang up the phone and only use the phone for emergency communications, as circuits are sure to be jammed with everyone calling everyone else. Do not tie up the lines with "Did you feel it?" calls.

Earthquakes can quickly to damage your home. But a thorough inspection can determine if it is safe for you and your family to go back inside.